The present invention relates generally to an actuator controller using a periodic signal for moving a movable portion of an actuator by a predetermined amount every one cycle of a periodic signal. More specifically, the invention relates to an actuator controller, which is made of a piezoelectric element and which is capable of driving an actuator, such as an inch warmer and a stepping motor, at a suitably controlled velocity.
A typical actuator, such as a stepping motor, comprises: a drive unit serving as driving means for moving or rotating a movable portion of an actuator by a predetermined amount when a given pulse is inputted thereto; a drive amplifier serving as power supply means for supplying an electric power to the drive unit on the basis of an inputted predetermined periodic signal; and periodic signal generating means for generating a periodic signal to be inputted to the drive amplifier. Therefore, in an actuator of this type (which will be hereinafter referred to as a "periodic signal driven actuator"), the moving amount of the movable portion of the actuator can be recognized by counting the cycle of the signal inputted to the drive amplifier. If no periodic signal is inputted, the movable portion of the actuator is not moved to be held by a fixed portion thereof. In view of this characteristic, the periodic signal driven actuator is suitably used for positioning or moving an object in accordance with a specific pattern.
In order to control the movement of an object by means of the periodic signal driven actuator, there is a typical method for detecting the position of the object by means of an external sensor or by counting the frequency of the periodic signal, to input a periodic signal having a given frequency or a given frequency pattern to the drive amplifier until the object reaches a predetermined position. Periodic signal generating means for generating the periodic signal often comprises a microcomputer. For example, Japanese Patent Application Laid-Open No. 7-23598 (1995) discloses that the frequency pattern of a motor driving pulse is generated in accordance with the position of a stepping motor to be supplied to a drive circuit block serving as a drive amplifier to drive a motor.
The periodic signal is often changed in accordance with physical conditions, which created by a moving object mounted on a movable portion of a stepping motor, to be inputted to a drive unit to drive an actuator. Japanese Patent Application Laid-Open No. 5-30402 (1993) discloses a periodic signal driven system utilizing a control method for carrying out the focus adjustment of a focus lens by means of a stepping motor.
However, the periodic signal driven system utilizing the control method triggers on the basis of the position of the object and the physical conditions to generate a given frequency or a given frequency pattern, so that there is a problem in that it is not possible to smoothly control the movement in accordance with the moving state of the object which changes every moment.
In addition, the frequency pattern as well as the position of the object and the physical conditions must be previously stored as data, so that there is a problem in that the required memory capacity increases in accordance with the precision and complexity required in control specifications.